Several sets of recombinant inbred strains will be maintained and used in a variety of genetic experiments. The RI strains will be typed for newly discovered polymorphisms that distinguish the two progenitor strains. The patterns of inheritance will be compared with previously determined patterns as a test for linkage. The strains will also be used for the genetic analysis of complex traits such as drug toxicity. The data generated will be used to judge the number of genes controlling susceptibility, potential linkages with marker genes, and pleiotropic effects of genes conferring susceptibility to different drugs. The RI strains will be made available to other investigators.